Ignitron welding timer



Patented Oct. 6, 1942 IGNITRON WELDING TIMER v Adolph H. Toepi'er, Wilkinsburg, Pa., assignor to Westinghouse Electric pany, East Pittsburgh,

Pennsylvania & Manufacturing Com- Pa., a corporation of Application March 23, 1939, Serial No. 263,741

17 Claims.

My invention relates to electric discharge apparatus and has particular relation to welding apparatus.

In resistance, spot and seam welding, it is desirable that the welding current be precisely determined. To accomplish this object, electric discharge valves are interposed between the alternating current source from which the current is supplied, and the material to be Welded. 'I'he valves are controlled in such manner that for each weld a predetermined number of half-cycles of current are supplied from the source and the current flow is initiated at instants in the corresponding half periods which are precisely fixed. An auxiliary valve, which is commonly designated as the timing valve, is connected to each of the main valves for the purpose of determining the number of halfcycles during which current ows. The instant in the half periods when current ow is initiated is determined by a second auxiliary valve designated as the heat control valve.

In apparatus constructed in accordance with the teachings of the prior art, of which I am aware, a timing valve, a heat control valve and the control element of the associated main valve are connected in series, the timing valve being connected to the control element of the main valve and the heat control valve Vbeing connected to the timing valve. Since current flow is, in general, initiated in the timing valve earlier than in the heat control valve, the latter is shunted by a resistor which should be selected of such magnitude that the current flow through the timing valve before the heat control valve is rendered conductive, is insuicient to render the corresponding main valve conductive. However, difliculties are often encountered in the selection of the resistor. If it is selected too small, it often happens that the main valves are rendered conductve by the current flow through the timing valve alone, and this difficulty is accentuated by the fact that the properties of the main valves sometimes change during operation. On the other hand, if the shunting resitance is selected too large, the timing valve often fails to become conductive when it should.

In the prior art arrangements, difficulties are also sometimes encountered in rendering the main valve conductive, when the instant at which -he conductivity is to be initiated is late in the half periods of the source. If the ignition angle of the heat control valve is greater than 90, the source potential is decreasing when the heat control valve is to be rendered conductive` Bocause of the negative rate of change of the anode-cathode potential which is thus impressed on the heat control valve and on the ignition electrode of the corresponding main valve the ring is unreliable. I angle of delay is 110, this diiculty is very pronounced.

It is, accordingly, an object of my invention to provide a Welding arrangement incorporating timing and heat control in which the main valve shall remain non-conductive when current flow is initiated in the timing valve before it is initiated in the heat control valve.

Another object of my invention is to provide a welding arrangement incorporating timing and heat control in which the main valves shall without fail become conductive at all times, regardless of how late in the half periods of the source the potential to initiate the conductivity of the heat control Valves is supplied.

A more general object of my invention is to provide apparatus for controlling the supply of power from a source to a load that requires energy in discrete impulses initiated at precisely set instants in which the timingof the energy supplied shall not spuriously affect the initiation of the power supply and the initiation of the power supply shall take place with certainty regardless of its characteristics.

In accordance with my invention, the positions which the heat control valves and the timing valves have in the ignition circuits of the main valves in the prior art arrangements are interchanged. That is to say, the heat control valve is connected to the control element of the main valve and the timing valve is connected to the heat control valve. The heat control valve and the control element of the main Valve are shunted by an impedance which carries the current of the timing valve before the heat control valve becomes conductive. This impedance may be a resistance, an inductor, or a capacitor if the only purpose of the arrangement is to prevent premature ignition of the main valves;J However, to provide for certainty in the ignition of the main valves when the iiring is late in the half-periods of the source, an impedance of the energy or charge storing type such as a capacitor is selected.

A capacitor connected to shunt the' heat control valve and the control element of the main valve is charged by the current flow through the timing valve before the heat control valve is rendered conductive. When the latter is rendered conductivathe capacitor potential is impressed have found that where the through the heat control valve on the ignition electrode of the corresponding main valve, and assures that the latter will become conductive at the desired instant. It is seen that essentially my invention contemplates the use of so-called anode firing of the main valve when the ignition is early in the half-periods of the source and independent firing by the potential supplied by a capacitor when the ignition is late in the halfperiods of the source. It is to be noted that the charging circuit of the capacitor is so selected 'that when the ignition is late the capacitor potential is substantially equivalent to the peak potentialvof the source. When the heat control Y,

valve is now rendered conductive late in the half period of the source, the potential impressed on the ignition electrode from the capacitor is the peak potential of the source, and no difilculties are encountered in rendering the main valve conductive.

f The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, 'will best be understood from the following description of a specific embodiment when read in connection with the accompanying drawing, in which the single figure is a diagrammmatic view showing a preferred embodiment of my invention.

The apparatus shown in the drawing comprises a welding transformer I across the secondary 3 of which a pair of Welding electrodes 5 are connected. The material 1 to be welded is disposed between the electrodes and when current fiows through the transformer the material is welded. The primary 9 of the transformer I is supplied from the line conductors I I and I3 of a source (not shown) which may be of the usual commercial 60-cycle type through a pair of ignitrons I5 and I1 connected in anti-parallel. While ignitrons I5 and I 1 are used in the preferred practice of my invention, they may be replaced by discharge devices of other types, for example, hot cathode arc discharge devices or mercury pool devices having collar ignition electrodes, without departing from the scope of my invention.

Each of the ignitrons I5 and I1 is provided with an anode I9, a cathode 2| and an ignition electrode 23. A pair of auxiliary valves 25 and 21 and 29 and 3| is associated with each ignitron I5 and I1, respectively, for the purpose of controlling its conductivity. One valve 25 and 29 of each pair is designed for heat control purposes, and the cathodes 33 of these valves are connected to the ignition electrodes 23 of the associated ignitrons I5 and I1. The other valve 21 and 3| of each pair is designed for timing purposes and the cathodes 35 of the latter are connected to the anodes 31 of the associated heat control valves 25 and 29, respectively. The anodes 39 of the timing valves are connected through corresponding movable contactors 4| and 43 of a starting relay 45, which are normally open, to the anodes I9 of the associated ignitrons I5 and Il, respectively, when the contactors are closed. The heat control valves 25 and 29 and the ignition electrodes 23 and cathodes 2| of the main valves I5 and I1, respectively, are in each case shunted by a network consisting of a resistor 41 and 49, respectively, and a capacitor 5| and 53, respective- 1y.

The Vtiming valves 21 and 3| are controlled from the usual timing system 55 which incorpo- 75 rates a start valve 51 and a stop valve 59. The heat control valves 25 and 29 are controlled from a phase shift network 6| lcomprising a resistor 09 and reactor 65 connected in series across the secondary 61 of a transformer 69 energized from a main supply. The phase angle in the half-priods of the source at which the heat control valves 25 and 29 are to be rendered conductive is preset by a voltage divider 1| connected bx tween an adjustable tap 13 of the reactor 65 and a tap 15 on the resistor 63. Control potential is directly impressed on the heat control valves 25 and 29 through control transformers 11 andv 19, respectively, the secondaries 8| of which a e connected between the control electrodes 83 and the cathodes .33 of associated heat control valves. The lower terminals of the primaries 85 of the transformers 11 and 19 are connected through a rheostat 91, the adjustable tap 89 of which is connected to the mid tap 9| of the secondary 61 of the transformer 69 supplying the phase shift network 6I. The remaining terminals of the primaries are connected together, and their connecting conductor 93 is connected to the adjustable tap 95 of the voltage divider 1|.

To initiate a welding operation, a circuit controller 91 such as a foot switch or a push button is closed and the starting relay 45 is energized. A contactor 99 of the relay 45 closes connecting the anodes |0| and |03 of the start valve 51 and the stop valve 59, respectively, to the positive terminal |05 of a direct current supply |01 energized from the main source through a full wave rectifier |09. The control electrode of the start valve 51 is connected to its cathode ||3 through a grid resistor II5, a full wave rectifier I I6 supplied from the secondary I1 of a peaking transformer ||9, a biasing source |2I, and a rheostat |23. Within a half period of the source following the closing of the contactor 99 and at an instant determined by the setting of a rheostat |25 connected to the primary |21 of the peaking transformer |I9, the start valve 51 is rendered conductive. Current is supplied in a circuit extending from the positive terminal |05 of the direct current supply |09 through the anode |0| and cathode ||3 of the start valve 51, a timing voltage divider |29, a resistor |3I, the conductor |33, to the negative terminal |35 of the direct current supply.

'I'he adjustable tap |31 of the voltage divider |29 is connected to the intermediate tap |39 of the secondary I4| of a transformer |43, the terminals of which are connected to the control electrodes |45 of the timing valves 21 and 3|. The cathodes 35 of the timing valves 21 and 3| are connected through corresponding resistors |41 and |49, respectively, and a common conductor |5| to an intermediate tap |53 of a voltage divider |55 across the direct current supply |01. Accordingly, when current flows through the timing voltage divider |29, a positive direct current potential is super-imposed on the potential supplied by the transformer |43 and the blocking potential supplied by the voltage divider |55 between the control electrodes |45 and the cathodes 35 of the timing valves 21 and 3| and the valves are rendered conductive during alternate half periods of the source.

When a timing valve 21 or 3| is in its turn 'first rendered conductive the corresponding circuit for the right-hand valve 3| extends from the left-hand line conductor I3, through a conductor |51, a conductor |59, a conductor |6|, the movable contactor 43 of the starting relay 45, a conductor |63, the anode 39 and the cathode 35 of the valve 3|, the resistor 49, the capacitor 53, a conductor |65, the primary 9 o1' the welding transformer I to the right-hand line conductor The circuit for the left-hand valve 21 is similar but, of course, extends through the corresponding capacitor 5|., The capacitors 5| and 53 are thus charged by the current flow through the timing valves 21 and 3l. The circuits/,f/for the timing valves which have just been traced do not include the ignition electrodes 23 of the ignitrons I5 and |1 and therefore there is no possibility of the premature ignition of the ignitrons.

At an instant predetermined by the setting of the phase shift voltage divider 95, energizing potentials are supplied to the heat control valves 25 and 29, and the heat control valves 25 or 29 associated with a conductive timing valve 21 or 3|, respectively, is rendered conductive at the present!y instant. If the energizing impulses are supplied early in the half-periods of the source, the heat control valves 25 and 29 are rendered conductive by the source potential. If the impulses are supplied late in the half-periods the potential of the capacitors 5| and 53 is such as to render the corresponding heat control valves 25 and 29 conductive. In either case, the heat control valves in their turn conduct current, short-circuiting the networks 41-5I and 49-53 and discharging the capacitors. Ihe current now ilows through the ignition electrodes 23 and the cathodes 2| of the corresponding ignitrons I5 and 1, the latter are rendered conductive in their turn and current is supplied to weld the material. When the ignition is late in the half-periods of the source, the capacitor potential which is then equal to the peak potential of the source is impressed across the ignition electrodes 2| and assures that Athe ignitrons 5 and |1 become conductive. The resistors 41 and 49 are provided for the purpose of limiting the peak current discharge through the heat control valves 25 and 29 to a valve within the current carrying capacity of the cathode. They may be replaced by inductances. The ignitrons |5 and |1 are rendered conductive during alternate half cycles of the source as long as the start valve is conductive.

The start valve 51 supplies current to charge a timing capacitor |61 which is connected in series with its anode |0| and cathode I3 through the rheostat |23. The capacitor |61 is also connected between the control electrode |69 and the cathode |1| of the stop valve 59, and after an interval of time predetermined by the rheostat |23, it attains a potential such that the stop valve 59 is rendered conductive. The current flow through the stop valve 59 reduces the potential across the start valve 51 to so low a value that a discharge is no longer maintained in the latter, and it is rendered nonconductive. As a result, current ow through the timing voltage divider |29 in series therewith ceases and the timing valves 21 and 3| are rendered non-conductive and interrupt the current ow through the ignition electrodes 23. The welding current is now interrupted and the welding operation is at an end.

Although I have shown and described certain specc embodiments of my invention, I am fully aware that many modifications thereof are possible. My invention therefore is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

I claim as my invention:

1. For use in supplying current to a load from a source, the combination comprising main valve means interposed between said source and said load, a first auxiliary valve means for conducting current to render said main valve means conductive, means for controlling the conductivity of said tlrst auxiliary valve means, a second auxiliary valve means for conducting current to render said main valve means conductive, said second valve means being connected in series with said first valve means, means for controlling the initiation of the conductivity of said second valve means, said second valve means being ,rendered conductive after said first valve means and both said auxiliary valve means conducting current when said main valve means is rendered conductive and means shunting said second valve means and said main valve means for conducting the current owing through said first valve means until said second valve means is rendered conductive.

2. For use in supplying current for welding a material from a source of alternating current, the combination comprising main valve means interposed between said source and said material, a iirst auxiliary valve means for conducting current to render said main valve means conductive, means for determining the number of half cycles of said source during which said first auxilia-ry valv means is conductive to determine the time during which welding current flows through said material, a second auxiliary valve means for conducting current to render said main valve means conductive, said second valve means being connected in series with said first valve means, means for determining the instant in the said number of half-cycles at which said second valve means is rendered conductive to control the heat supplied for welding said material, and means shunting said second valve means and said main valve means for conducting the current ilowing through said rst valve means until said second valve means is rendered conductive.

3. For use in supplying current to a load from a source, the combination comprising main valve means interposed between said source and said load, and having discharge initiating means which initiates a discharge when current is supplied thereto, a ilrst auxiliary valve means for conducting current to render said main valve means conductive, means for controlling the conductivity of said first auxiliary valve means, a second auxiliary valve means for conducting current to render said main valve means conductive, said rst valve means, said second valve means and said discharge initiating means being ccnnected in series, means for controlling the initiation of the conductivity of said second valve means, said second valve means being rendered conductive after said rst valve means, and means, shunting said second valve means and said discharge initiating means, for conducting the current ilowing through said rst valve means until said second valve means is rendered conductive.

means interposed betweensaid source and said load, and having discharge initiating' means which initiates a discharge when-currentlfis supsecond auxiliary valve means for conducting current to render said main valve means conductive, said rst valve means, said second valve means and said discharge initiating means being connected in series, means for controlling the initiation of the conductivity of said second valve means, said second valve means being rendered conductive after said lirst valve means, and means including charge storing means shunting said second valve means and said discharge initiating means for conducting the current flowing through said iirst valve means until said second valve means is rendered conductive.

5. For use in supplying current to a load from a source, the combination comprising main valve vmeans interposed between said source and said load,. and having discharge intiating means which initiates a discharge when current isisupplied thereto, a iirst auxiliary valve means for conducting current to render said main valve means conductive, means for controlling the conductivity of said first auxiliary valve means, a second auxiliary valve means for conductingcurrent to render said main valve means conductive, said rst valve means, said second valve means and said discharge initiating means being connected in series, means for controlling the initiation of the conductivity of said second valve means, said second valve means beingrendered conductive after said first valve means, and a circuit including charge storing means shunting said second valve and said discharge initiating means, said circuit having an impedance such that said charge storing means is charged to a potential suiicient to render said main valve means conductive when applied through said second valve means in thelinterval of time between the rendering conductive of said iirst valve means and the rendering conductive of said second valve means.

6. In combination, a iirst valve means, means for controlling the conductivity of said rst valve means, a second valve means connected in series with said iirst valve means, means for controlling the conductivity of said second valve means to render it conductive after said first valve means, said valve means to conduct together when said second valve means .is rendered conductive, and a circuit including charge storing means shunting said secondvalve means to conduct the current of said rst valve means until said second valve means is to be rendered conductive and then to supply a potential tending to render said second valve means conductive.

'7. In combination with a source and a load to be supplied from said source, an ignitron having an anode, a cathode and an ignition electrode interposed between said source and said load, a iirst auxiliary valve having an anode connected to the anode of said ignitron .and a cathode, a second auxiliaryvalve having an anode connected to the cathode of said first auxiliary valve and a cathode connected to the cathode of said ignitron, anda capacitor connected between the anode and the cathode .ofA said second auxiliary valve.

8. In combination with a source and a load to be supplied from said source, an ignitron having an anode, a cathode and an ignition electrode interposed between said source and said load, a

iirst auxiliary valve having an anode connected,

to the anode of said ignitron and a cathode, a second auxiliary valve having an anode connected to the cathode of said rst auxiliary valve and a cathode connected to the cathode of said ignitron, a, capacitor connected between the anode of said second auxiliary valve and the cathode of said ignitron and control means for said auxiliary valves functioning to render said second valve conductive after said rst valve.

l 9. In combination with a source fof alternating current and a load to be supplied from said source, a pair of ignitrons each having an anode, a cathode and an ignition electrode connected in anti-parallel between said source and said load, a pair of iirst auxiliary valves each having an anode connected to the anode of a corresponding ignitron and a cathode, a pair of second auxiliary valves each having an anode connected to the cathode of a corresponding first auxiliary valve and a cathode connected to the cathode of the ignitron to the anode of which said anode of the corresponding iirst valve is connected and a capacitor connected between the anode of each second auxiliary valve and the cathode of the corresponding ignitron.

10.111 combination with a source of alternating current and a load to be supplied from said source, a pair of ignitrons each having an anode, a cathode and an ignition electrode connected in anti-parallel between said source and said load, a pair of rst auxiliary valves each having an anode connected to the anode of a corresponding ignitron and a cathode, a pair of second auxiliary valves each having an anode connected to the cathode of a corresponding first auxiliary valve and a cathode connected to the cathode of the ignitron to the anode of which said anode of the corresponding first valve is connected, a capacitor connected between the anode of each second auxiliary valve and the cathode of each associated ignitron, control means for said first auxiliary valves -for determining the number of half periods of said source during which said iirst valves are conductive and control means for said second auxiliary valves for determining the instants in said half periods at which said second valves are rendered conductive.

11. The method of rendering conductive an -ignitron supplied with potential from an alternating current source at diiierent instants in the half periods of the source which comprises using .anode firing to render the ignitron conductive during the iirst quarter cycle of a period and using condenser ring to render the ignitron conductive during the second quarter cycle of a period.

12. For use in supplying current to a load from an alternating current source, the combination comprising an ignitron interposed between said load and said source, said ignitron having an anode, a cathode and an ignition electrode, an auxiliary valve having a pair of principal electrodes, asymmetrlcally conductive impedance means connecting the principal electrodes of said auxiliary valve between the anode and the ignition electrode of the ignitron and a circuit including charge storing means shunting said valve and the ignition electrode of .said ignitron. said circuit and said asymmetrically conductive means having a total impedance such that when the charging of said storing means is initiated at the zero potential point of a half cycle of said source, said charge storing means is charged substanto the peak potential of said source in an interval of time of the order of a quarter period of said source.

13. For use in supplying current to a load from a source, the combination comprising an ignitron interposed between said load and said source, said ignitron having an anode, a cathode and an ignition electron, an auxiliary valve having an anode and a cathode, asymmetrically conductive impedance means connecting the anode of said auxiliary valve to the anode of said ignitron, means connecting the cathode ofsaid auxiliary valve to the ignition electrode of said ignitron and charge storing means connected between the anode of said auxiliary valve and the cathode of said ignitron.

14. For use in supplying power from a source I oi' alternating current to a load the combination comprising a pair of ignitrons each having an anode, a cathode, and an ignition electrode connected in anti-parallel between said source and said load, a pair of auxiliary electric discharge valves connected in series between the anode and the ignition electrode of one of said ignitrons, another pair of auxiliary electric discharge valves connected in series between the anode and the ignition electrode of the other ignitron and impedance means interconnecting the junction points of said pairs of auxiliary valves.

15. For use in supplying power from a source of alternating current to a load the combination comprising a pair of ignitrons each having an anode, a cathode. and an ignition electrode connected in anti-parallel between said source and said load, a pair of auxiliary electric discharge valves connected in series between the anode and the ignition electrode of one oi said ignitrons, another pair oi' auxiliary electric discharge valves connected in series between the anode and the ig- -nition electrode of the other ignitron and connections for impressing a control potential interposed between the junction points of said pairs of valves.

16. For use in supplying power from a source of alternating current to a load the combination comprising a pair or ignitrons each having an anode, a cathode, and an ignition electrode connected in anti-parallel between said source and said load, a pair of auxiliary electric discharge, valves connected in series between the anode and the ignition electrode of one of said ignitrons, another pair of auxiliary electric discharge valves connected in series between the anode and the ignition electrode of the other ignitron and connections for impressing a potential for timing the conductivity of said'ignitron interposed between the junction points of said pairs of valves.

17. For use in supplying power from a source of alternating current to a load the combination comprising a pair of ignitrons each having an anode, a cathode, and an ignition electrode connected in anti-parallel between said source and said load, a pair of auxiliary electric discharge valves connected in series between the anode and the ignition electrode of one of said ignitrons, another pair of auxiliary electric discharge valves connected in sexies between the anode and the ignition electrode of the other ignitron, means for impressing impulses to render each of these valves of said pairs that are connected to the anodes o! said ignitrons conductive at predetermined instants in the hal! period of said source, and connections for impressing a potential for timing the conductivity of said ignitrons interposed between the Junction points of said pairs oi' valves.

v ADOLPH H. TOEPFER. 

